1. Technical Field
The present disclosure relates to a package structure and manufacturing method thereof and, more particularly, to a light emitting diode (LED) package structure and manufacturing method thereof.
2. Description of Related Art
LEDs are a type of illumination component comprised of III-V semiconductor materials. In general, LEDs have advantages such as long life, compact size, high shock resistance, low heat generation and low power consumption. Therefore, LEDs have been widely used in the home and a variety of equipment indicators and light sources. In recent years, development of LEDs is moving towards multi-color and high brightness, and thus the fields of application have been extended to large outdoor billboards, traffic lights, and related fields. In the future, LEDs may even become both power-saving and eco-friendly lighting source.
For example, most of the high-power white LED packages utilize one or more blue LEDs with yellow phosphor. The reason why a white LED emits white light is because its LED chip emits blue light. When blue light transmits through yellow phosphor it is converted into yellow light, and white light is formed when the yellow light converted by yellow phosphor is mixed with blue light that is not converted to yellow light. As the blue light emitted by blue LEDs has a certain degree of directivity, intensity of the part of the emitted blue light which has a larger angle of deviation from the optical axis of the LED tends to be weaker. This tends to result in the intensity of yellow light larger than the intensity of blue light at larger angles of deviation from the optical axis of the LED. As a result, a yellow halo is formed around the edge of the illuminated area of the luminaire. Additionally, uneven distribution of yellow phosphor on LEDs in the manufacturing process of white LEDs that utilize blue LED with yellow phosphor also results in yellow halo around the white light emitted by LEDs thus manufactured. This affects the uniformity of the color of light emitted by white LEDs.
Therefore, a conventional approach is to add brightener in the phosphor powder in order to reduce the incidence of yellow halo, where the brightener may be white particles or glass particles. This approach scatters the beam of light emitted by the LED to reduce the extent of the yellow halo. However, the effect achieved by the addition of brightener is often at the expense of the overall light extraction efficiency of the LED, and tends to produce no positive effect in terms of enhancing color rendering performance of the LED.